Gas burner

ABSTRACT

A gas burner ( 100 ) is described including a variable speed fan ( 104 ) controlled to give an optimum gas/air mixture. The control is provided using a microprocessor with the gas valve position or measured characteristics of the output flame as feedback. The gas burners includes improved outlet slots to ensure optimum flame contact with a cooking vessel.

SUMMARY OF THE PRIOR ART

[0001] There are a number of apparatus known in the art for using gasheating as a means of cooking. An important part of such apparatus, isthe gas burner which provides the outlet for the gaseous fuels, whichare then combusted to generate heat. Thus a number of methods have beendevised to improve the operating characteristics of such gas burnersover time.

[0002] For example it is known in the art to pressurise the air supplyto the burner. In U.S. Pat. No. 4,622,946 for instance, a gas burner isdescribed with one fixed speed fan on the burner inlet and both the gasand air flow is controlled by a valve which supplies multiple burners.It is also known to use a fan to extract the exhaust gases from theburner, where the combustion takes place in an enclosed space such asdescribed in U.S. Pat. No. 5,800,157 and also European PatentApplication No. 801270. Also in European Patent Application No.887590 agas burner is described with gas and air fed through orifices (ofmatched sizes) into a mixing chamber with a fan pressurising the flowwhich is supplied to the burner head.

[0003] It is also known in the art to vary the shape of the outlet portsto improve operation. For example in U.S. Pat. No. 5,649,822 and PCTPatent Application No. 98/15780 gas burners are disclosed with angledoutlet ports. In U.S. Pat. No. 5,800,159 a gas burner is describedincluding flared stability ports. It is also known to have a gas burnerwith flare in vertical plane of the outlet ports and substantialcircumferential area in, for example, German Patent No. 4427953

[0004] However, while these prior art systems do provide improvements incertain areas of operation, they are not suited for use with a range ofgas supplies, may be large or expensive to manufacture, and may notprovide distributed flame contact with the heating vessel.

[0005] It is an object of the present invention to provide an improvedgas burner which goes someway to overcoming the above mentioneddisadvantages or which will at least give the public a useful choice.

SUMMARY OF THE INVENTION

[0006] Accordingly in a first aspect the present invention consists in agas burner comprising

[0007] a burner housing including at least one internal cavity and atleast three openings, all being in fluid communication with saidinternal cavity,

[0008] an outlet assembly including a number of outlet ports in fluidcommunication with said a first of said openings, and a burner capattached to said outlet assembly,

[0009] adjustable gases supply means for providing an adjustable flow ofgaseous fuels, in fluid communication with a second of said openings,

[0010] oxygen supply means for providing a flow of gases at leastcontaining oxygen, in fluid communication with a third of said openings,and

[0011] pressurisation means associated with said third opening forpressurising said flow of gases at least containing oxygen,

[0012] wherein in use pressurisation means causing said flow of gases atleast containing oxygen to flow through said internal cavity and mixwith said adjustable flow of gaseous fuels, the combination thereofflowing through said first opening and then said number of outlet portsto be combusted, and said adjustable gases supply means being readilyaccessible and removable, through the removal of said outlet assembly.

[0013] Preferably said pressurisation means comprises a variable speedfan.

[0014] Preferably said outlet assembly includes a venturi through whichsaid adjustable flow of gaseous fuels flows, thereby causing said flowof gases at least containing oxygen to mix with said flow of gaseousfuels.

[0015] Preferably said gas burner further comprises control means andmeans for supplying a variable relating to the gases flow rate of saidflow of gaseous fuels to said control means, whereby said control meansvaries the energisation of said pressurisation means according to saidvariable.

[0016] Preferably said burner housing includes a spiral voluteconnecting said first opening to said second opening.

[0017] In a further aspect the present invention consists in a gasburner comprising,

[0018] a burner housing including at least one internal cavity and atleast three openings, all being in fluid communication with saidinternal cavity,

[0019] an outlet assembly including a number of outlet ports in fluidcommunication with said a first of said openings, said number of outletports encompassing a substantial portion of the outer circumference ofsaid outlet assembly around number of outlet ports,

[0020] adjustable gases supply means for providing an adjustable flow ofgaseous fuels, in fluid communication with a second of said openings,and

[0021] oxygen supply means for providing a flow of gases at leastcontaining oxygen, in fluid communication with a third of said openings,

[0022] wherein in use said flow of gases at least containing oxygenflows through said internal cavity and mixes with said adjustable flowof gaseous fuels, the combination thereof flowing through said firstopening and the said number of outlet ports to be combusted.

[0023] Preferably the total commutative width of said number of outletports is greater than 70% of the outer circumference of said outletassembly around number of outlet ports.

[0024] Preferably the vertical height of said number of outlet ports isless than 2 mm.

[0025] Preferably the vertical height of said number of outlet ports is1 mm.

[0026] Preferably each of said number of outlet ports are angled at aradial angle greater than 0 degrees.

[0027] Preferably each of said number of outlet ports are angled at aradial angle between 40 to 50 degrees.

[0028] Preferably each of said number of outlet ports are flaredoutwards.

[0029] Preferably each of said number of outlet ports are flaredoutwards at between 6 and 12 degrees.

[0030] To those skilled in the art to which the invention relates, manychanges in construction and widely differing embodiments andapplications of the invention will suggest themselves without departingfrom the scope of the invention as defined in the appended claims. Thedisclosures and the descriptions herein are purely illustrative and arenot intended to be in any sense limiting.

[0031] The invention consists in the forgoing and also envisagesconstructions of which the following gives examples.

BRIEF DESCRIPTION OF THE DRAWINGS

[0032] One preferred form of the present invention will now be describedwith reference to the accompanying drawings in which;

[0033]FIG. 1 is a cross section of the gas burner according to thepreferred embodiment of the present invention,

[0034]FIG. 2 is a cross section of the outlet assembly according to thepreferred embodiment of the present invention,

[0035]FIG. 3 is a perspective view of the outlet assembly according tothe preferred embodiment of the present invention,

[0036]FIG. 4 is a blown out perspective of the gas and air intakemanifold according to the preferred embodiment of the present invention,

[0037]FIG. 5A is a plan views of the outlet assembly according to thepreferred embodiment of the present invention,

[0038]FIG. 5B is an enlarged plan view of the outlet ports according tothe preferred embodiment of the present invention,

[0039]FIG. 6 is a cross section of an outlet assembly according to analternative embodiment of the present invention, and

[0040]FIG. 7 is a block diagram illustrating the control strategy forthe variable speed fan.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0041] The present invention provides an improved gas burner whichprovides lower emissions, a greater operating range and improvedperformance over that of prior art gas burners. The present inventionincludes a variable speed fan to pressurise the air supply to be mixedwith the gas for combustion. The present invention also includesinnovative outlet ports which improve the quality and distribution ofthe output flame over a greater operating range as compared to the priorart devices.

[0042] Referring now to FIGS. 1 to 4 the gas burner 100 is comprised ofa main body 102, a variable speed fan 104, an outlet assembly 106 and aburner cap 108. The main body 102 also includes a top cover 103 which isattached on top of the main body during manufacture using bolts 97 whichscrew into prethreaded holes 115 in the main body 102. This 2 partstructure is to allow the fan 104 to be located in slots 105 and lockedin place without the need for further bolts. The entire gas burner 100,is attached to the top face plate 95 of a gas appliance by a helicallythreaded locking nut 107 which threads onto the outer thread 110 of thetop cover 103 which forces the face plate 95 down onto the top cover103. The outlet assembly 106 is shown in more detail in FIGS. 2 and 3which slides down in place atop the top cover 103. Similarly the burnercap 108 is positioned atop the outlet assembly 106.

[0043] The gas supply is connected to the main gas inlet 109 on theexterior of the main body 102. This connects through to a gas inletorifice 111 positioned at bottom of a central chamber 113 in the mainbody 102 directly below the outlet cylinder 114. The gas jet fitting 112screws into the gas inlet orifice 111. It will be appreciated that thepresent invention is modular whereby different output ranges can beachieved by the replacement of outlet assembly 106 with one of a rangeof interchangeable assemblies. Such assemblies range in size accordingto maximum output, but have the same inner dimensions to be fittedinterchangeably to the same main body 102. Further modularity isachieved by the ability to replace the gas jet fitting 112 as requiredfor different gas supplies eg: LPG versus natural gas. Similarlymaintenance and cleaning are also simplified by this modularity, andsimple construction.

[0044] In order for the gas to mix adequately with the air supply thepresent invention includes a venturi 116 is formed by the underside ofthe burner cap 108 and the upper face of the outlet assembly 106. Theventuri effect result from the convergence of the flow path at the topof the outlet cylinder 114, followed by a horizontal, divergence 120.This venturi effect draws in the air in with the gas flow.

[0045] The air supply pressurised by the fan 104, follows a flow pathbest shown in FIG. 4. The air swirls horizontally through a spiralvolute 122, which terminates in the central cavity 113. At this point asthe gas is jetted up from the gas jet fitting 112 up into the venturi116, the combination of the venturi action, and the mixing action of theswirling pressurised air, causes the air and gases to mix thoroughly.

[0046] In the preferred embodiment of the present invention the variablespeed fan is controlled as shown in FIG. 7. A controller 200, either amicroprocessor or any analogue equivalent, receives a signal from arotary encoder 202 on the gas inlet valve 204 feeding the gas burner. Itwill be appreciated other sensors such as polentiometer or microswitches on a corn could equally be used. Based on a stored formula orlookup tables 205, the controller adjusts the energisation 206 of thefan 208 depending on the setting of the gas valve. Alternatively the fanspeed could be controlled based on actual flow rate of the gas asmeasured by a flow rate sensor. A further alternative would be closedloop control using direct feedback from the flame. The flame could bemeasured using CO₂, O₂, colour of light emitted etc and matched againstoptimum levels to decide whether a higher or lower flow of air isrequired.

[0047] After the venturi 116, the gases/air mixture flows through theoutlet ports 124, formed by grooves 126 in the outer periphery of theupper face of the outlet assembly 106 and the underside of the burnercap 108. Once the gas/air mixture flows through the ports 124 out intothe atmosphere it combusts forming the characteristic ring flame aroundthe circumference 128 of the burner head.

[0048] The grooves 126, shown in more detail in FIGS. 5A and 5B have anumber of distinguishing features. The grooves 126 are characterised inthat they occupy greater than 70% of the circumference 128 of the burnerhead. Each quarter of the outlet assembly 106, has a groove 142 at anangle of 40° 146 at one end and a groove 140 at an angle of 50° 144 atthe other end. All the grooves in between are at angles increasingevenly from 40° and 50°. The grooves 126 are all angled at a range ofangles to ensure that none of the flames significantly impinge on thetrivet 129 as this will result in carbon monoxide production. Intraditional burners a groove is missed where the trivet is. In thepreferred embodiment of the present invention the trivet 129 ispositioned in the wide space 131 between the quarterly transitionbetween groove angling. In FIG. 5A the trivet 129 is shown at an angleof 45° between a groove 142 at 40° and a groove 140 at 50°. Thisconfiguration allows more even heating and since the ports are stillclose together they can light each other. Just inside the grooves 126,is an annular channel 147. This acts as a pressure buffer zone, whichstabilises the gas flow from any variations in the supply pressurebefore being combusted.

[0049] The grooves 126 themselves are also carefully designed in shape.The inlet cross section 132 is of the same height as the outlet crosssection 134 which are both approximately 1 mm, but the outlet port crosssection 134 area is approximately 1.6 times that of the inlet crosssection 132. The flaring from inlet to outlet is 11 degrees, but canrange from approximately 6 to 12 degrees. This gives a ratio of 3.5 to4.5 of the groove length to the inlet width. The inlet cross section 132is effectively a semi-circle whereas the outlet cross section 134 hasrounded portions 136, 137 at either end connected by a flat portion 138in the centre. Both the rounding and flaring are designed to give goodflame shape for a wide range of burner output levels.

[0050] In an alternative embodiment of the present invention the outletassembly 152, is shown in FIG. 6 with a vertical venturi. Similarly tothe preceding embodiment, the venturi include a narrowed section 150,followed by a slowly diverging section 160. Again this arrangementcauses the flow of gas through the venturi to draw in air which mixeswith the gas before combustion. In all other aspects this embodimentoperates as for the preferred embodiment.

[0051] It will be appreciated by the foregoing the present inventionpresents a number of advantages over the prior art.

[0052] Gain in operating range of burner. Typical gas burners may have aturndown ration as low as 3:1 and while the best gas burners may achievesay 6:1 whereas electric elements are typically are better than 10:1.The present invention provides a burner with which ratios of better than20:1 maybe achieved. The upper limit is increased by the use of thevariable speed fan. Also the shaping of ports helps reduce gas velocitywhich helps flame to remain attached to the burner and not blow out athigher rates while the small cross sectional area allows the burner tobe turned down low without burning back;

[0053] Reduced emissions and better efficiency from improved combustion;

[0054] Ability to change the jet of the burner from above without havingto disassemble the product;

[0055] Ease of assembly/construction;

[0056] Increased efficiency due to increased flame contact with thecooking vessel.

[0057] The Burner is smaller than traditional burners for a givenoutput, giving a significant increase in efficiency due to more flame incontact with a given size pot. Also reduces the “cold spot” in themiddle of the burner.

1. A gas burner comprising: a burner housing including at least oneinternal cavity and at least three openings, all being in fluidcommunication with said internal cavity, an outlet assembly including anumber of outlet ports in fluid communication with said a first of saidopenings, and a burner cap attached to said outlet assembly, adjustablegases supply means for providing an adjustable flow of gaseous fuels, influid communication with a second of said openings, oxygen supply meansfor providing a flow of gases at least containing oxygen, in fluidcommunication with a third of said openings, and pressurisation meansassociated with said third opening for pressurising said flow of gasesat least containing oxygen, wherein in use pressurisation means causingsaid flow of gases at least containing oxygen to flow through saidinternal cavity and mix with said adjustable flow of gaseous fuels, thecombination thereof flowing through said first opening and then saidnumber of outlet ports to be combusted, and said adjustable gases supplymeans being readily accessible and removable, through the removal ofsaid outlet assembly.
 2. A gas burner as claimed in claim 1 wherein saidpressurisation means comprises a variable speed fan.
 3. A gas burner asclaimed in claims 1 or 2 wherein said outlet assembly includes a venturithrough which said adjustable flow of gaseous fuels flows, therebycausing said flow of gases at least containing oxygen to mix with saidflow of gaseous fuels.
 4. A gas burner as claimed in any one of claims 1to 3 further comprising control means and means for supplying a variablerelating to the gases flow rate of said flow of gaseous fuels to saidcontrol means, whereby said control means varies the energisation ofsaid pressurisation means according to said variable.
 5. A gas burner asclaimed in any one of claims 1 to 4 wherein said burner housing includesa spiral volute connecting said first opening to said second opening. 6.A gas burner comprising: a burner housing including at least oneinternal cavity and at least three openings, all being in fluidcommunication with said internal cavity, an outlet assembly including anumber of outlet ports in fluid communication with said a first of saidopenings, said number of outlet ports encompassing a substantial portionof the outer circumference of said outlet assembly around number ofoutlet ports, adjustable gases supply means for providing an adjustableflow of gaseous fuels, in fluid communication with a second of saidopenings, and oxygen supply means for providing a flow of gases at leastcontaining oxygen, in fluid communication with a third of said openings,wherein in use said flow of gases at least containing oxygen flowsthrough said internal cavity and mixes with said adjustable flow ofgaseous fuels, the combination thereof flowing through said firstopening and the said number of outlet ports to be combusted.
 7. A gasburner as claimed in claim 6 wherein the total commutative width of saidnumber of outlet ports is greater than 70% of the outer circumference ofsaid outlet assembly around number of outlet ports.
 8. A gas burner asclaimed in claim 6 or 7 wherein the vertical height of said number ofoutlet ports is less than 2 mm.
 9. A gas burner as claimed in claim 8wherein the vertical height of said number of outlet ports is 1 mm. 10.A gas burner as claimed in any one of claims 6 to 9 wherein each of saidnumber of outlet ports are angled at a radial angle greater than 0degrees.
 11. A gas burner as claimed in claim 10 wherein each of saidnumber of outlet ports are angled at a radial angle between 40 to 50degrees.
 12. A gas burner as claimed in claim 11 wherein said number ofoutlet ports are divided into a number of sections, there being a spaceon the outer circumference of said outlet assembly between outlet portsat the opposing limits of adjacent sections, said space adapted to inuse permit a finger of a trivet juxtaposed directly above said spacewithout the flames from said outlet ports substantially impinging onsaid finger.
 13. A gas burner as claimed in any one of 6 to 12 whereineach of said number of outlet ports are flared outwards.
 14. A gasburner as claimed in claim 13 wherein each of said number of outletports are flared outwards at between 6 and 12 degrees.
 14. A gas burnersubstantially as described herein and with reference to and asillustrated by the accompanying drawings.